We plan to continue to study the mechanisms for augumented synthesis of cholesteryl ester in atherosclerotic microsomes. In this connection we intend to investigate the propensity of individual serum lipoproteins from normal and cholesterol-fed rabbits to enrich normal microsomes with cholesterol and to examine their influence on the cholesterol-esterifying (ACCAT) activity. We plan to investigate the requirement of phosphatide for the activation of cholesterol-esterifying activity of normal aortic and liver microsomes. We intend to study uptake and utilization of fatty acid by normal and atherosclerotic aortas at varying molar ratios.